Wednesday, September 25, 2024
Arm and Movement Angles
(Click to embiggen)
LEFT IMAGE
On the left image, the compass-like layout is showing the arm angle of every pitcher, with Zack Wheeler highlighted. The average angle for all of Wheeler's pitches is 27 degrees. The arm angle is measured in two dimensions, based on when the ball is released, and relative to the shoulder at that point in time.
The high arm slot pitchers are over 60 degrees, for both RHP (oRange circles) and LHP (purpLe circles). Pure sidearmers are at 0 degrees either way.
Small note: for LHP, you will see I put in parentheses an angle following the Cartesian plane standard. So, 0 degrees for a LHP is shown also as 180 degrees, while 60 degrees for a LHP is shown also as 120 degrees. This will become clear in a moment why I did that.
MIDDLE IMAGE
In the middle chart, we see the movement of all of Wheeler's pitches. Wheeler throws his sinker with an arm angle of 24 degrees (somewhat similar to the 27 degrees he throws all his pitches). That dark gray line represents his arm angle of 24 degrees.
Also on that chart is a dark orange line that goes to the center of his sinker movement chart: that represents the angle of movement of his sinker, which is 21 degrees.
As you can see, the angle of movement of his sinker is somewhat close to the angle of his arm. Logically, there would have to be some kind of relationship between how you throw your pitches and how a ball moves. The arm angle is just one factor. How the ball rolls off the fingers would be another, and this would be most obvious with sliders. And another one: by manipulating the orientation of the seams, you can trigger the airflow around the ball to push the ball in a certain direction more than it would otherwise move (aka Seam-Shifted Wake or SSW).
TOP RIGHT
The top right chart plots all of the release angles you see from the left chart (using the Cartesian standard) on the x-axis, along with the movement angle (that middle chart, but for the sinkers of all pitchers) on the y-axis. As you can see, there is a strong 1:1 relationship between arm angle and movement angle (for sinkers). Some of the pitchers buck the trend, like Tyler Rogers (that bottom left circle), with an arm angle of minus 65 degrees, but a movement angle of minus 84 degrees, for a 19 degree deviation.
BOTTOM RIGHT
The bottom right chart keeps the x-axis of the top chart and shows the y-axis as the movement angle minus the arm angle. In other words, how much deviation is there in the sinker movement, relative to the arm angle. Here, it becomes a bit clearer that there is additional movement arm-side.
- For RHP, the average arm angle is 34 degrees, while the movement angle is 28.5 degrees, so there's an average of 5.5 degrees of deviation, an extra 5.5 degrees of drop (or sink, hence the term sinker).
- For LHP, the average arm angle is 33 degrees (or 147 in Cartesian), with an extra 5.6 degrees of sink.
And this is how arm angle and movement angle relate to each other, for sinkers.
***
I actually had wanted to start this for 4-seam fastballs, but there were a few pitchers that were way off. In looking at those pitchers, it became clear the reason: they were likely throwing cutters, not 4-seam fastballs. While we investigate those pitchers, I turned my attention to sinkers to better illustrate the concept.
***
Fans of Matt Lentzner may remember this article from 15 years ago at Hardball Times, as a precursor to his Pitching Peanut (slideshow or powerpoint).